pub fn print_if_else() -> ()
{
    let n: i64 = 13;
    let big_n: i64 = if n < 10 && n > -10
    {
        10 * n// 一定要记住结尾不带有分号！！！
    }
    else
    {
        n / 2
    };
    println!("{}", big_n);
}